The incidence of fungal infections has increased at an alarming rate in the past two decades. Most of this increase is due to opportunistic fungal infections related to the growing population of people with weakened immune systems due to HIV, cancer, and other diseases; and to modern medical practices such as the use of intensive chemotherapy and drugs that suppress the immune system. However, fungal infections like vaginal yeast infections and athlete's foot are common in healthy people, too.
In this section, we will cover a variety of fungal infections affecting both those with weakened immune systems and healthy people.
Fungi are everywhere—as moulds, they grow in homes and on foods; as yeasts, they are found in foods and in our bodies. Even mushrooms are classified as fungi—although most of them are quite harmless. Whatever form fungi take, they survive by breaking down organic matter. Only 180 of the 250,000 known species of fungi can cause disease in people.
An opportunistic infection is caused by an organism that normally lives in our body or our environment and causes no damage, but takes advantage of the opportunity a weakened immune system gives it to cause disease.
Many different kinds of fungi live inside the human body in peaceful equilibrium with it. When the body's immune system is weakened due to an illness such as AIDS or treatment such as chemotherapy, the balance can be disturbed, allowing fungi to cause disease. Such diseases are called opportunistic infections.
People most often come into contact with fungi in the organisms' natural habitats. Because many fungi live in the ground, gardeners are often at risk for fungal infections. The organisms can enter the body through bare feet, hands, or other exposed areas. Different kinds of fungi live in different geographic areas. For example, cocci is a disease of the Southwestern United States and is found in people who live in or visit this area.